1. Field of the Invention
The invention relates to a driving assistance device and a driving assistance method for assisting a driver in driving a vehicle.
2. Description of the Related Art
A variety of driving assistance techniques for assisting the driver have been suggested and put to practical use in order to increase safety and reduce a workload on a driver of a vehicle such as a passenger automobile, a truck, or a bus. In one of such driving assistance techniques that has been suggested and put to practical use, the vehicle is prevented from departing from a traffic lane, for example, by steering assist conducted on the basis of information relating to surrounding environment of the vehicle, such as information relating to a lane in the traveling direction of the vehicle. For example, Japanese Patent Application Publication No. 2001-1921 (JP-A-2001-1921, paragraphs [0005] and [0022]) describes a technique for establishing a target trajectory of a host vehicle and controlling the actuator so as to come close to the target trajectory.
However, with a driving assistance technique, driving control of the vehicle has to be performed according to the driver's intention. Therefore, the driving control that is automatically executed in the driving assistance control is required to comply with the driver's intention. The automatic driving control of the vehicle, such as the lane keep control that has heretofore been suggested, is not changed till the driver operates the vehicle by himself. Accordingly, the driver's intention is difficult to be incorporated in the driving control of the vehicle, and a conflict between the driving control following the driver's intention and the driving assistance control can occur in the control device.
As a result, the driver feels uncomfortable and the operation feeling can be degraded. With the technique described in JP-A-2001-1921, if the driver operates the vehicle when the driving assistance is executed, the driving assistance control to control the vehicle to travel along the target trajectory that has been generated in advance may contradict the driver's intention, and thus the driver may feel uncomfortable and the operation feeling may degrade. With this respect, such a driving assistance technique can be improved.